Biomedical subjects

C F van Swol

Publications and source records attributed to C F van Swol.

10 recordsLinked to original sources

PubMed2001

Development of an MR-safe tracking catheter with a laser-driven tip coil.

We developed a magnetic resonance (MR)-safe tracking catheter using an optical fiber with a light-diffusing tip segment to transport laser energy through the catheter. This energy is converted to a DC current running through a small coil at the catheter tip. Our method is inherently MR-safe since the use of long conducting wires is avoided. The intravoxel dephasing induced by the tip coil was clearly visible for laser powers between 250 mW and 750 mW for all angular positions of the catheter. J. Magn. Reson. Imaging 2001;13:131-135.

Catheterization↗

PubMed2001

Contact laser-assisted neuroendoscopy can be performed safely by using pretreated 'black' fibre tips: experimental data.

BACKGROUND AND OBJECTIVE: Laser-assisted endoscopic neurosurgery by using conventional fibres requires the use of high-power laser light. Because this is potentially hazardous, we developed a pretreated fibre tip and evaluated tissue effects in vitro and in vivo. STUDY DESIGN/MATERIALS AND METHODS: By applying a highly absorbing coating to the front of the ball tip, almost all laser light is transformed into thermal energy, instantly producing ablative temperatures at the tip itself. The temperature distribution was examined by using an in vitro thermal imaging technique. The in vivo effect on rabbit cerebral tissue was examined macroscopically and histologically. RESULTS: By using a conventional fibre tip, ablation was not observed, despite the use of high energy and power (20 W for 10 seconds), whereas histology and thermal imaging demonstrated deleterious effects deeply into the cerebral tissue. By using the coated fibre tip, ablation was observed at low energy and power (1 W for 1 second) with thermal effects restricted to superficial structures. CONCLUSIONS: We show that laser-assisted neuroendoscopy can only be considered to be safe when pretreated "black" fibre tips are used, as laser light damages deep structures.

Animals↗

PubMed1999

Electrovaporization as a treatment modality for transurethral resection of the prostate: influence of generator type.

OBJECTIVES: To study the influence of the electrosurgical generator on the vaporization efficacy during electrovaporization (EVAP) using different vaporization elements. METHODS: Electrical properties of human prostatic (in vivo) and bovine myocardium (in vitro) tissue were measured under electroresection and electrovaporization conditions. The effective output power of four different generators ("old generation" Force 4 and Force 40 and "new generation" Force 300 and Force FX) was measured at different impedance loads. In vitro, the coagulation and vaporization capabilities of the electrosurgical generators in combination with resection and vaporization elements were studied on homogeneous tissue (bovine myocardium). RESULTS: The electrical impedance of human prostatic tissue and bovine myocardium increases from 400 to 1000 ohms when coagulated. The effective output power of the old generation electrosurgical devices depends strongly on tissue impedance. This implies that working on already coagulated tissue using such devices is not well controlled and not reproducible. By contrast, new generation electrosurgical devices correct for the higher impedance of coagulated tissue, thus delivering constant output power and corresponding tissue effects. CONCLUSIONS: For an effective application of the EVAP technique, the use of a new generation impedance independent electrosurgical unit is highly recommended.

Animals↗

PubMed1998

Influence of decay of laser fibers during laser prostatectomy on clinical results.

Three types of sidefiring laser fibers (34 Urolase, 20 Ultraline, and 114 Prolase II) were visually inspected after a laser prostatectomy, and transmission measurements were performed using a power meter (Aquarius). The results were correlated with the clinical outcome. Despite differences in the amount of loss in transmission for the fibers used, we could not establish any significant effect on clinical outcome measures, such as improvement in maximal flow rate or symptom score. The visual aspect of the Urolase fibers was significantly related to the amount of transmission loss, whereas no such relation was found for the other two types of fibers. Prostate size and the total amount of energy delivered by the laser source also did not correlate with the clinical outcome. To determine the relation between the energy absorbed by the prostate and clinical outcome, a large number of patients must be evaluated, and any factor that can be controlled needs to be monitored. For the latter, the power meter as presented here is a useful complementary tool.

Diuresis↗

PubMed1998

Laser-assisted neuroendoscopy using a neodymium-yttrium aluminum garnet or diode contact laser with pretreated fiber tips.

OBJECT: Although lasers have proved to be valuable in neuroendoscopy, surgeons are still not comfortable using high-energy laser endoscopic probes in proximity to vital structures such as the basilar artery in third ventriculostomy. The authors have developed a special laser catheter for use in neuroendoscopy; the object of this paper is to present their experimental and clinical experiences using the catheter. METHODS: This laser catheter is fitted with an atraumatic ball-shaped fiber tip that is pretreated with a layer of carbon particles. These carbon particles absorb approximately 90% of the energy emitted, which is very effectively converted into heat. As the heat is generated in this very thin layer of carbon coating, the temperature at the surface of the ball-shaped tip reaches ablative temperatures instantly at powers of only a few watts per second, which has enabled the authors to limit drastically the amount of laser light used and the length of exposure needed, thereby increasing safety even around critical structures. CONCLUSIONS: The authors present experimental data and their clinical experience using these pretreated fiber tips with a neodymium-yttrium aluminum garnet contact laser or a diode contact laser in 49 patients (22 males and 27 females) and a variety of procedures: third ventriculocistemostomy (33 patients), cyst fenestration (nine patients), colloid cyst resection (six patients), and fenestration of the septum pellucidum (one patient). There was no instance of mortality or increased morbidity. To date, the procedure success rate is 100% and the overall outcome success rate is 86%. The authors conclude that pretreated atraumatic ball-shaped fiber tips now make laser application safe and effective in a variety of neuroendoscopic procedures. Because of their low power range (only several watts), compact diode lasers will be the energy source of first choice.

Adolescent↗

PubMed1997

Laser light delivery systems for medical applications.

For medical applications, the choice of a delivery system will be governed by the characteristics of the laser system on the one hand and the tissue application on the other. The most important parts are the beam guide and the target optics. Most lasers have wavelengths in the visible and near-infrared and can be transported by silica fibres. For the mid- and far-IR other fibre materials or hollow waveguides are used. At the end of the waveguide or fibre, an optically active component is present to direct the beam and to control the power density on the target tissue. The laser beam can be delivered either by focusing handpieces and scanning devices to treat superficial areas or through microscopes, endoscopes and flexible fibres to treat areas almost anywhere inside the human body. The characteristics of the delivery systems can be determined looking at beam properties, transmission and thermal properties. The delivery of continuous wave or pulsed laser energy, contact or non-contact, will determine the contribution of optical, thermal and mechanical effects to the tissue. The practical use of laser delivery systems is illustrated by various clinical applications.

Diagnostic Imaging↗

PubMed1995

Side-firing devices for laser prostatectomy. An overview.

Transurethral laser coagulation of the prostate has become an accepted treatment for benign prostatic hyperplasia (BPH). The most common method is the use of a sideward-firing fiber that, once inserted in the prostatic area, irradiates the abundant prostatic tissue with Nd:YAG laser light. In this study, eight different side-firing fibers that are commercially available were evaluated. The devices can be characterized by the way laser light is deflected sideward and by their thermal behavior. Most of the eight devices differ with regard to the angle at which the laser beam is deflected, the spot size on the irradiated tissue surface, and the heating of the device itself. Implementation of the optical and thermal characteristics of each device in the treatment protocol will contribute to the optimal use of laser energy for prostatectomy.

Equipment Design↗

PubMed1995

Laser prostatectomy for patients with benign prostatic hyperplasia: a prospective randomized study comparing two different techniques using the Prolase-II fiber.

Laser prostatectomy for patients with complaints due to benign prostatic hyperplasia is a relatively new treatment option. The most effective procedure for coagulation and vaporization of the prostate is not yet known. In a prospective randomized study of 30 patients, 2 techniques for the delivery of laser energy were compared at 40 W for 90 s. The complications were minimal and antegrade ejaculation was preserved in 15 of 18 potent men. In 24 patients urodynamics evaluation was possible. In both groups a significant reduction in the symptom score was observed. The decrease in detrusor pressure at maximal flow and the increase in flow rate were, however, disappointing. No significant difference in the results was found between the two groups. The power setting needs to be changed in further studies.

Aged↗

PubMed1994

[Laser prostatectomy as alternative to transurethral prostate resection in benign prostatic hyperplasia].

OBJECTIVE: Assessment of the results of laser prostatectomy, as a treatment for benign prostatic hyperplasia (BPH). DESIGN: Prospective case control study. SETTING: University Hospital Utrecht, the Netherlands. METHOD: Between February 1992 and May 1993, 54 men with their micturition complaints due to BPH were treated with laser prostatectomy (TULIP system). Results were assessed using the international prostatic symptom score (IPSS), the maximal flow and urodynamic tests. The results were compared retrospectively with results of transurethral resection of the prostate (TURP; n = 40): both groups were urodynamically identical. RESULTS: Of the 54 patients, 10 could not be evaluated 6 months after treatment (5 of them underwent TURP or a second laser prostatectomy). In 40 patients complete evaluation including urodynamics before and six months after treatment was possible. A significant decrease in the symptom score from 19.3 (SD: 7.6) to 6.3 (SD: 5.4) and increase of the maximal flow during pressure-flow studies from 9.6 to 15.8 ml per second were observed. The decrease of the voiding pressure at 6 months after TURP in comparison with laser prostatectomy was close to significance (p = 0.05); the other improvements after urodynamics were comparable. CONCLUSION: Laser prostatectomy is a promising new therapy for BPH.

Aged↗

PubMed1994

Optimization of laser prostatectomy.

A recent development in the treatment of Benign Prostatic Hyperplasia (BPH) is the use of a side firing fiber device coupled with a Nd:YAG laser. In this study, a numerical and an in-vitro model were developed to calculate and visualize the temperature distribution and the associated tissue necrosis due to irradiation of the prostate with Nd:YAG laser light. Different irradiation modalities were included: a static beam, with the irradiating fiber remaining at one place and a moving beam, with the fiber scanning over the surface at different speeds. Also blood vessels were incorporated in the model and showed to have major influence on the resulting tissue necrosis.

Computer Simulation↗